| We measure the branching fraction of the exclusive charmless semileptonic decay B → oℓnuℓ, where ℓ is either an electron or a muon, with the charged B meson recoiling against a tag B meson decaying in the charmed semileptonic modes B → Dℓnuℓ or B → D*ℓnuℓ. The measurement is based on a dataset of 426.1 fb-1 of e+e- collisions at a CM energy of 10.58 GeV recorded with the BABAR detector at the PEP-II asymmetric B Factory located at the SLAC National Accelerator Laboratory. We also calculate the relevant B → o hadronic form factors to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element ∣Vub∣. |