  This work presents accurate {\it ab initio} investigations of various
spectroscopic properties of a few Li-like ions in presence of a plasma
environment within the Debye screening potential. The coupled-cluster theory in
the relativistic framework has been employed to compute ionization potentials,
excitation energies, electric dipole oscillator strengths, and electric
quadrupole transition probabilities of Li-like C$^{3+}$, N$^{4+}$, and O$^{5+}$
ions. The unretarded Breit interaction has been implemented to increase the
accuracy of the calculations. The effects of ion density and temperature on the
ionization potentials, excitation energies, electric dipole oscillator
strengths, and electric quadrupole transition probabilities have been
investigated in the plasma environment. It is found that the plasma screening
leads to a sharp decrease in the ionization potential as the screening strength
increases. With increasing strength, the oscillator strengths associated with
2$s ^{2}S_{1/2}$$\rightarrow2 p ^{2}P_{1/2, 3/2}$ transitions increase, whereas
the transition probabilities associated with 3$d ^2D_{3/2, 5/2}$$\rightarrow2 s
^2S_{1/2}$ transitions decrease.
