  Double layer quantum systems are promising platforms for realizing novel
quantum phases. Here, we report a study of quantum oscillations (QOs) in a
weakly coupled double layer system, composed of a large angle twisted double
bilayer graphene (TDBG). We observe two different QOs at low temperature, one
with a periodicity in carrier density (n), i.e. Shubnikov de Haas oscillation
(SdHO) due to Landau quantization, and the other one in displacement field (D),
resulting a grid pattern. We quantify the interlayer coupling strength by
measuring the interlayer capacitance from the grid pattern with a capacitance
model, revealing an electron hole asymmetry. At high temperature when SdHO are
thermal smeared, we observe resistance peaks when LLs from two minivalleys in
the moir\'e Brillion zone are aligned, regardless of carrier density;
eventually, it results in a two fold increase of oscillating frequency in D,
serving as a smoking gun evidence of the magneto intersubband oscillations
(MISO) in a double layer system. The temperature dependence of MISO suggests
electron-electron interaction between two minivalleys play a crucial rule in
the scattering, and the scattering times obtained from MISO thermal damping are
found to be correlated with the interlayer coupling strength. Our study reveals
an intriguing interplay among Landau quantization, moir\'e band structure, and
scatterings.
