Affirmed by published opinion. Judge GREGORY wrote the opinion, in which Judge TRAXLER and Judge KING joined.
*283 OPINION
On July 26, 2001, Betty Anne Osborne (“Osborne”) entered a guilty plea before a magistrate judge to one count of conspiring to possess with intent to distribute cocaine and cocaine base. On appeal, Osborne challenges: 1) the quantity of drugs attributed to her for sentencing purposes; and 2) the district judge’s failure to conduct de novo review of the Rule 11 proceedings conducted by the magistrate judge. As explained below, the court did not err in determining the quantity of drugs attributable to Osborne, and a district judge is not required, absent a defendant’s request, to review de novo the Rule 11 proceedings conducted by a magistrate judge. Thus, we affirm Osborne’s conviction and sentence. 1
I.
During the execution of a search warrant, government agents discovered illegal drugs in Osborne’s home. On Osborne’s person, the agents found four grams of cocaine base. Further, Osborne’s co-defendant, for whom she “cooked” cocaine into crack for the distribution thereof, was found to be in possession of more than six grams of cocaine base.
Osborne pleaded guilty to one count of conspiracy to possess with the intent to distribute five grams or more but less than fifty grams of cocaine base, in violation of 21 U.S.C. § 846. Osborne waived her right to enter a guilty plea before a district judge, and consented to have a magistrate judge accept her plea. The magistrate judge conducted a plea hearing pursuant to Fed.R.Crim.P. 11, in which he determined that there was a factual basis for Osborne’s conviction. Upon accepting her guilty plea, the magistrate judge advised Osborne:
[T]he district judge retains control and jurisdiction over your case, and that the matter of acceptance or rejection of your plea agreement and the matter of sentencing will be left to the district judge. Any perceived deficiencies in this hearing or any other matters that you may have will be taken up with the district judge at the time of sentencing.
Finally, the magistrate judge informed Osborne that, at sentencing, the district court would rely upon a written presentence re *284 port (“PSR”), to which her counsel would have an opportunity to object.
At the sentencing hearing, the district judge invited Osborne to object to or comment upon the PSR. Osborne declined, and the district judge adopted the statements contained in the PSR as its findings of fact for sentencing. The PSR reflected Osborne’s admission of responsibility for the charged offense, and it recommended the related sentencing adjustment. Based upon the PSR, the district judge found that Osborne had a total offense level of 31, with a criminal history category of VI, yielding a sentencing range of 188 to 235 months. The district judge orally sentenced Osborne to 180 months. However, the district judge’s written order entering judgment reflected a sentence of 188 months. At no time prior to this appeal did Osborne challenge the quantity of drugs attributed to her for sentencing purposes, nor did she object to the magistrate judge’s authority to conduct the Rule 11 proceedings in her case.
II.
Because this is the first time that Osborne has challenged the quantity of drugs attributed to her for sentencing purposes, we review this issue only for plain error.
United States v. Olano,
Likewise, Osborne never requested that the district judge review the magistrate judge’s authority to conduct Rule 11 proceedings, and she did not initially raise this issue on appeal.
Sua sponte,
we directed the parties to file supplemental briefs on the issue. We did so because we have an independent duty to assess jurisdictional issues, and we deem it appropriate in this case to consider the scope of a magistrate judge’s authority to conduct Rule 11 proceedings.
See United States v. Dees,
III.
This appeal presents two issues: 1) whether the district court correctly calculated the quantity of drugs attributable to Osborne for sentencing purposes; and 2) whether the district court erred in failing to review de novo the Rule 11 proceedings conducted by the magistrate judge.
A.
We first assess whether the district court correctly calculated the quantity of drugs attributable to Osborne for sentencing purposes. This issue is easily disposed of pursuant to standard principles of derivative liability. A conspirator may be held accountable for all quantities of drugs attributable to the conspiracy so long as it was reasonably foreseeable that the drugs would be involved in the conspiracy and that the drugs were possessed within the scope of the conspiratorial agreement. See United States v. Gilliam, 987 F.2d *285 1009, 1013 (4th Cir.1993). Osborne admitted to processing cocaine base into crack cocaine for her co-defendant’s distribution operation. At the time of her arrest, over ten grams of crack cocaine were found in her residence — either in her possession or in her co-defendant’s possession. Under these circumstances, the district court did not err in sentencing Osborne for possession of five or more grams of crack cocaine.
B.
In order to assess whether the district judge erred in accepting Osborne’s plea without conducting de novo review thereof, we must first consider whether the Federal Magistrates Act, 28 U.S.C. §§ 631-639 (1988) (the “Act”), authorizes a magistrate judge to preside over Rule 11 proceedings. Second, we must determine whether Article III of the Constitution requires a district judge to conduct de novo review of such proceedings, irrespective of a defendant’s request for such review. As all of our sister circuits have determined, we conclude that the Act, pursuant to its “additional duties” clause, 28 U.S.C. § 636(b)(3), authorizes magistrate judges to conduct Rule 11 proceedings. Further, we hold that a district judge need not review such proceedings de novo unless a defendant requests such review. 3
1. Statutory Authorization
Every circuit to have considered whether the Act authorizes a magistrate judge to conduct Rule 11 proceedings has held that the Act permits such a delegation.
See Reyna-Tapia,
In assessing the statutory question, we begin with the Supreme Court’s decision in
Peretz.
There, the Court held that a magistrate judge may, if the defendant so consents, conduct
voir dire
in a criminal case.
Id.
at 932-37,
By contrast, in
Peretz,
where the defendant agreed to allow the magistrate judge to preside over the
voir dire
proceedings, the Court concluded that the Act authorizes such a delegation.
Applying Peretz’s approach to “additional duties,” our sister circuits have uniformly concluded that the Act authorizes a magistrate judge to preside over Rule 11 proceedings. For example, the Second Circuit, in
United States v. Williams,
concluded that magistrate judges possess the statutory authority to conduct Rule 11 proceedings.
In
United States v. Ciapponi,
the Tenth Circuit likewise held that the Act authorizes a magistrate judge to conduct Rule 11 proceedings.
Similarly, in
United States v. Dees,
the Fifth Circuit concluded that a magistrate judge has the statutory authority, pursuant to the “additional duties” clause of the Act, to preside over Rule 11 proceedings.
Finally, the Ninth Circuit, sitting
en banc,
in
United States v. Reyna-Tapia,
recently decided that the Act authorizes magistrate judges to conduct Rule 11 proceedings.
Like our sister circuits, we look to the approach developed by the Court in
Per-etz.
The supervision of Rule 11 plea proceedings, while obviously requiring care and discretion to ensure that guilty pleas rest upon a firm factual basis, hardly
*288
dwells nigh the outlands of magistrature.
4
Applying the “additional duties” test developed in
Peretz,
we observe that allowing a magistrate judge to supervise
voir dire
proceedings in a felony trial implicates far greater discretion than the delegation of Rule 11 responsibilities. At the same time, we note that, because both processes are fraught with constitutional concerns, a defendant must clearly waive his right to have such proceedings conducted by an Article III judge.
See Bryson,
2. Constitutionality and De Novo Review
Having determined that the Act’s “additional duties” clause authorizes a magistrate judge to conduct Rule 11 proceedings, we must assess whether this statutory grant is consistent with Article III of the Constitution.
5
In resolving this question affirmatively with respect to
voir dire,
the Supreme Court in
Per-etz
examined two separate constitutional issues: 1) a defendant’s right to the presence of an Article III judge at critical phases of trial; and 2) the structural integrity of the judiciary.
Second, turning to consider whether the delegation implicates the structural integrity of the judiciary, the Supreme Court discussed its earlier approval, in
United States v. Raddatz,
When a matter is referred, the judge may freely reject the magistrate’s recommendation. He may rehear the evidence in whole or in part. He may call for additional findings or otherwise recommit the matter to the magistrate with instructions. Moreover, the magistrate himself is subject to the Art. Ill judge’s control. Magistrates are appointed by district judges, and subject to removal by them.
Peretz,
Considering the matter at hand, we again note that there is little relevant precedent regarding the constitutionality of “additional duties” clause delegations in this Circuit. In particular, we have never considered whether Rule 11 proceedings may be delegated to a magistrate judge. 8 *290 Under Peretz, we are bound to decide whether the availability of de novo review suffices here to safeguard the integrity of constitutional courts. Osborne could have requested review by the district judge of her Rule 11 plea proceeding. However, she did not. Had the district judge denied such a request, we would have before us a fundamentally different case. Hence, like the Ninth and Tenth Circuits, both of which held that de novo review is not required where the defendant clearly consents to entering a plea before a magistrate judge and raises no objection to the Rule 11 plea proceeding, we hold that unless the defendant requests such review or objects to some aspect of the magistrate judge’s plea colloquy, a district judge is not bound to conduct de novo review. That is, there is no entitlement to de novo review absent a request therefor.
IV.
Finding no error in the quantity of drugs upon which Osborne’s sentence was based, and finding no obligation of the district court to review the magistrate’s Rule 11 colloquy, we hereby
AFFIRM.
Notes
. Osborne also challenges her 188-month sentence. We note that there is a discrepancy between the 188-month sentence entered in the written criminal judgment and the sentence of 180 months that the district judge pronounced orally at the sentencing hearing. It is normally the rule that where a conflict exists between an orally pronounced sentence and the written judgment, the oral sentence will control.
See, e.g., United States v. Morse,
. We note that the Tenth Circuit has held that it will apply the plain error rule “less rigidly” when reviewing constitutional issues not raised during trial.
United States v. Ciapponi,
. We note that only two of our sister circuits, the Ninth Circuit in
United States v. Reyna-Tapia,
. By contrast, in
United States v. Bryson,
. Section 1 of Article III vests the judicial power in "one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish.” U.S. Const. Art. Ill, § 1. The Supreme Court has interpreted this provision to limit Congress’s ability to vest judicial authority in non-Article III judges.
See, e.g., Northern Pipeline Constr. Co. v. Marathon Pipe Line Co.,
. Of course, a challenge to the waiver itself, upon the appropriate showing of error, maybe raised after a plea has been entered — a factual predicate not before us today.
. The power of the district judge to review a magistrate judge’s performance of delegated duties will help to assure protection of the defendant’s constitutional liberties.
. Unfortunately, one may read the opinions of our sister circuits on this issue and come away wanting some degree of clarification. In
Torres,
for example, the Eighth Circuit wrote that the Second
(United States v. Williams,
