A key figure in the investigation of alleged drug use on Capitol Hill who pleaded guilty here last June to drug-distribution charges was arrested yesterday in Bethesda and held in jail in Baltimore on new drug charges, law enforcement officials said.

Douglas W. Marshall, 27, a former Capitol page whose arrest in April 1982 sparked the Capitol Hill probe, had been free on bond pending sentencing in U.S. District Court in Washington on a charge of conspiracy to distribute cocaine. Marshall, who is scheduled to be sentenced on Monday, faces a maximum penalty of 15 years in prison on that charge.

Marshall was charged yesterday with attempting to possess cocaine for distribution and possession of the drug with intent to distribute it, according to a spokesman for the federal Drug Enforcement Administration.

In an affidavit filed in U.S. District Court in Baltimore by DEA agent John Coleman, the agent said that DEA learned in August that Marshall was interested in buying cocaine and worked with an informant to arrange a sale.

Marshall allegedly received one gram of cocaine from the informant on Aug. 26 to give to potential buyers as a sample for a planned sale of one pound of the drug, according to Coleman's affidavit.

Prosecutors in Baltimore asked that Marshall be held on a $100,000 bond, but no hearing had been set as of last night.

Marshall and Troy M. Todd Jr., 23, of Potomac, were first arrested along with a third man in Marshall's Northwest Washington home after allegedly selling eight ounces of cocaine to an undercover D.C. police officer. Both men fled the country shortly before their indictment by a federal grand jury in November, 1982. They were rearrested in Perth, Australia, in January 1983 and returned to this country last April.

Their arrests sparked Justice Department and congressional investigations of alleged drug use by congressmen and Capitol Hill aides. The Justice Department, after investigating the allegations, last July declined to prosecute any congressmen, but two House employes implicated in the probe have pleaded guilty to drug charges.

Although the Justice Department has ended its investigation, a special House ethics committee investigation headed by attorney Joseph A. Califano Jr. is continuing.