  In this study we present photometric and spectroscopic variation analysis and
orbital period study of a low-mass interacting system OO Aql. Simultaneous
solution of the light and radial velocity curves provide us a determination of
new set of stellar physical parameters for the primary and the secondary
companion as M$_{1}$ = 1.05(2) M$_{\odot}$, M$_{2}$ = 0.89(2) M$_{\odot}$,
R$_{1}$ = 1.38(2) R$_{\odot}$, R$_{2}$ = 1.28(2) R$_{\odot}$,
$\log{(L_1/L_{\odot})} = 0.258$ and $\log{(L_2/L_{\odot})} = 0.117$ and the
separation of the components were determined a = 3.333(16) R$_{\odot}$. Newly
obtained parameters yield the distance of the system as 136(8) pc. Analyses of
the mid-eclipse times indicate a period increase of $\frac{P}{\dot{P}}=4\times
10^{7}$ yr that can be interpreted in terms of the mass transfer
$\frac{dM}{dt}=5\times 10^{-8}$ M$_{\odot}$/yr from the less massive component
to the more massive component. Our new solution confirmed that OO Aql is a
multiple system in the form of AB + C + D. We found initial astrophysical
parameters for the component of the system and its current age to be 8.6 Gyr
using nonconservative stellar evolution model (EV-TWIN code).
